A probe card is an interface between an electronic test system and a semiconductor wafer. Its purpose is to provide an electrical path between the test system and the circuits on the wafer, thereby permitting the testing and validation of the circuits at the wafer level, usually before they are diced and packaged. That is, before hundreds of IC chips fixed on a wafer are diced into chips with a few square millimeters, “Wafer Test” should be performed utilizing such probe card to check quality of IC chips and thus screen out defectives. However, as semiconductor manufacturers continue to shrink die geometries, which makes the task of on-wafer testing increasingly more difficult since pitches between bonding pads are becoming minute. Probe card with innovative solutions, which can perform a wafer level probing test on multiple chips on a wafer at once or even on the whole wafer, are required to meet the semiconductor industry's test needs so as to ensure higher accuracy and repeatable wafer testing and thus increase yield as well as lower cost.
Probe cards are broadly classified into cantilever type, vertical type, and MEMS (Micro Electro-Mechanical System) type depending on shape and forms of contact elements. The cantilever type is represented by the epoxy ring probe card, the vertical type is represented by the cobra probe card, and the MEMS type is usually used for DRAM (dynamic random access memory) testing.
Among which, although the cantilever type probe cards are usually designed with fine pitch as small as 40 μm, it is only suitable for testing those wafers 100, 200 with bonding pads 110, 210 configured at the edges thereof, as shown in FIG. 1 and FIG. 2, so that the pin count of such cantilever type probe card is limited and thus it is classified as low-end probe card. As for the vertical type probe card, it is originated from a manufacturing process disclosed in 1977 in U.S. Pat. No. 4,027,935, entitled “Contact for an electrical contactor assembly”, in which a vertical probe head disclosed has each of ifs probes buckle or deflect when a predetermined axial load is applied thereto for enabling the same force to be exerted on each of a plurality of pads on a semiconductor chip as it is being tested. However, although such vertical type probe card is adapted for testing wafers 300 with a plurality of bonding pads arranged as arrays and is classified as high-end probe card with high pin count, it is bottlenecked for designing such vertical type probe card with pitch as small as 100 μm. Therefore, such vertical type probe cards are only good for testing flip chip packaged IC.
It is noted that each pin in the foregoing two types of probe card are manufactured in a manner that it is fixed onto a PCB (printed circuit board) manually. Thus, their manufacturing cost is closely related to their pin counts, i.e. the higher the pin count is, the higher the manufacturing cost will be.
The MEMS type probe card for DRAM is exemplified in the U.S. Pat. No. 5,476,211, entitled “Method of manufacturing electrical contacts, using a sacrificial member”, and the U.S. Pat. No. 5,476,211, entitled “Method of making and using lithographic contact springs”. However, it is disadvantageous in that its manufacturing process is complex and it is bottlenecked for designing such MEMS type probe card with pitch smaller than 70 μm, thereby, such MEMS type probe can be very expensive. In addition, it is limited to be used for testing wafers with bonding pad arrangement similar to that shown in FIG. 1.
Over all, those currently available probe cards are all capable of performing wafer testing in a “one pin corresponding to one pad” manner, so that it is required to redesign its pin configuration for matching wafers of various bonding pad arrangements. In addition, the pin pitches of those currently available probe cards are limited by their manufacturing processes, which might not be able to meet the challenge of ultra fine pitch up to those smaller than 70 μm, high pin counts and full wafer testing. There are already some studies trying to deal with shortcomings, such as high cost, pins of large volume, and restricted shape, etc, that are common for those conventional probe cards as they are usually manufactured by mold casting, drawing or roll milling. Such studies can be exemplified by the probe card manufacturing methods disclosed in TW Pat. No. 90107441 and TW Pat. No. 93107026. However, such studies still limited in the aforesaid “one pin corresponding to one pad” manner, and thus suffer the same shortcomings. Therefore, it is in need of a new probe card that not only is not troubled by the aforesaid fine pitch bottleneck, but also can be configured with high pin count and manufactured at low cost.